Epidemiological Study Designs.pptx
- 1. Epidemiological Study Designs Dr Jazeela Mohamed Siddique Senior resident Department Of Community Medicine
- 2. Introduction • Study designs directs how investigation is conducted • methods used in research to gather the data needed to explore a research question Research question Study design Data collection Data Analysis Result interpretation
- 3. Classification Observational studies Descriptive studies Analytical studies Experimental studies Randomized controlled trials Field trials Community trials
- 4. Observational studies • Careful observations • Allow natural course of events • Investigator measures but does not intervene • direct control of investigator • Intervention in experimental group • Compare outcome with control group Experimental studies
- 5. Descriptive studies • Observing the distribution of disease in a population • Identifying the characteristics associated with the disease • Generate hypothesis Case reports Case series Cross sectional studies Longitudinal studies Ecologic studies describe
- 6. Case reports Detailed presentation of a single case • New or unfamiliar diseases • Rare manifestations
- 7. Case series • Study of larger group of patients (> 10) with a particular disease • Common way of delineating the clinical pictures of a disease • Absence of a comparison group
- 8. Cross sectional studies (Prevalence studies) • Observation of a snapshot of a population at a single point in time • Unit of observation and analysis: The individual • Exposure and disease outcome are determined at same time • Observation for the presence of: o One or more outcomes o One or more exposures • Do not know disease duration; temporal sequence of exposure – disease
- 9. Longitudinal studies • Observation of the same population at several points of time • Unit of observation and analysis: The individual • Change over time can be tracked • Observation of • Relation between exposure and outcome • Outcome of exposure over different lengths of time
- 10. Ecologic studies (Correlational studies) • Unit of analysis : group (population) • Relate whether populations with high rates of disease also have high rates of exposure • Ecologic fallacy : relations at group level is not possessed by individuals of the group
- 11. Analytical studies • Test hypothesis • Measures the pattern of exposure and disease • Inference by comparing groups Cross sectional studies Case control studies Cohort studies compare
- 12. Analytical Cross sectional studies • Prevalence distribution of exposure and outcome • Comparison of outcome differences in exposed and unexposed
- 13. Case control studies (Retrospective studies) • Starts by picking cases and controls • Exposure and outcome occurred before start of study • Backward looking study (effect cause)
- 14. Cohort studies • Cohorts are identified before outcome occurs • Study groups observed over a time period • Forward looking study (causeeffect)
- 15. Randomized controlled trials • Randomly assigns participants into experimental and control group • Intervention in experimental group • The groups are followed up to measure the outcome of intervention • Blinding Reference population Experimental group Control group
- 16. Summary Observational studies Experimental studies Descriptive studies • Case reports • Case series • Cross-sectional studies • Longitudinal studies • Ecologic studies Randomized controlled trial Field trial Community trial Analytical studies • Cross-sectional studies • Case control studies • Cohort studies
- 17. THANK YOU